8 May
2021
8 May
'21
5:32 p.m.
On 5/8/21 12:00 PM, cctalk-request at classiccmp.org wrote:
Message: 8 Date: Fri, 7 May 2021 21:59:08 +0000 From:
W2HX
<w2hx at w2hx.com> To: Andrew Back <andrew at carrierdetect.com>,
"General
Discussion: On-Topic and Off-Topic Posts" <cctalk at classiccmp.org>
Subject: RE: 400 Hz Message-ID:
<de37431b96cf4c82ba5ddb2b9daf1873 at EXBE015SV3.NA02.MSEXCHANGEOUTLOOK.COM>
Content-Type: text/plain; charset="utf-8" I will add that aircraft are
one of the main users of 400 Hz. This is because weight is always an
critical design consideration. So with smaller transformers, smaller
capacitors, etc, you can save a LOT of weight on electronic devices in
an aircraft. 73 Eugene W2HX -----Original Message----- From: cctalk
<cctalk-bounces at classiccmp.org> On Behalf Of Andrew Back via cctalk
Sent: Wednesday, May 5, 2021 11:26 AM To: cctalk at classiccmp.org
Subject: Re: 400 Hz On 05/05/2021 16:07, Grant Taylor via cctalk wrote:
That's a very neat repackaging of the Lambda power supplies! Do they
have the surge capability to start that rotary inverter (which may
require a LOT more than 44 amps until the armature gets moving)... I
hope you tested them first ;)
I bought a 1 KVA 115V 400 Hz supply, a PP-7482/G from Fair Radio back
when they still had them ("Reparable") a few years ago. The H-bridge
TO-3 transistors were all blown, some with holes melted through their
lids. I replaced them with BUX48A parts and it works again. It really
sings that A-flat though ;)
But I don't have anything to run with it! When I was young, 400 Hz
surplus gear was a dime a dozen because no one had 400 Hz power. Now I
do and all that gear has disappeared...
-Charles
WB3JOK/0 since '76 :)
Were the higher frequencies used because it
directly effected the
amount of time / duration in (fractions of) seconds between peaks of
rectified (but not yet smoothed) power?
Haven't read the rest of the thread
and so at the risk of being profoundly wrong... Benefit of 400Hz mains is that
transformers can be much smaller. Think of switching power supplies that rectify to DC and
then switch up into kHz, which are then able to use far smaller transformer cores than an
old linear PSU. At least this is a key motivation with 115V/400Hz 3-phase aviation power
AFAIK.
By coincidence we've just built a big 28VDC power supply, so that we can run a
vintage 400Hz aircraft rotary inverter, which will then be used to power up old mil
surplus kit that wants this. A classic adventure in yak shaving. Anyway, here's the
28VDC bit.
https://www.rs-online.com/designspark/constructing-a-high-current-28v-dc-po…